The field of wireless communications has seen a significant growth in the communication standards and protocols used for audio, video and data communication. Mobile devices incorporate antenna systems that are adaptable to the various communication standards and protocols. The various communication standards and protocols typically exist over a broad frequency spectrum such as 1.8 Gigahertz (GHz) for Global System for Mobile Communications (GSM), 2.5 GHz for Bluetooth™, 3.5 GHz for Worldwide Interoperability for Microwave Access (WiMax) and 5.2 GHz for Wireless Local Area Network (WLAN) technologies. As a result, the antenna systems need to support signals of the various frequency bands for effective communication. A key to effective communication is to design a filtenna design coupled to the antenna system that filters out out-band interferences and noises present in a wideband spectrum.
Existing methods for filtering out out-band interferences and noises involve using a band stop filter that suppresses undesired frequency signals. Several techniques and structures such as cavity filters, dielectric body embodiments, surface integrated waveguides, high impedance surface, frequency selective surfaces have been used to suppress undesired signals reaching an antenna system. Some techniques involve use of large number of diodes and radio frequency (RF) Micro-Electro-Mechanical Systems (MEMS) switches for achieving frequency selectivity and spectral efficiency. However aforementioned structures are typically complex in design and include complex biasing mechanisms and increase an overall cost of the antenna systems. Further, frequency selectivity by existing filtering techniques achieved only for higher frequencies. Furthermore, some techniques in the field of cognitive radio applications involve use of separate modules are integrated in a single substrate for spectrum sensing and to communicate with RF bands. However such integration leads to large volume and bulky structures.
Hence, there is a need for a multi band reconfigurable filtenna design of less complexity to filter out band interferences. Also there is a need for a filtenna design that provides high spectral efficiency and frequency selectivity. Hence an alternative and economical multi band reconfigurable filtenna design for antenna systems is proposed.